1. Field of the Invention
The present invention relates to a new type anti-amnestic agent. More particularly, the present invention relates to a new type anti-amnestic agent containing a specific prolinal derivative as an active ingredient thereof.
2. Description of the Prior Art
In recent years, it has been made clear that vasopressin, oxytocin and the like peptide hormones participate in memory. B. Bohus et al. report that the administration of such peptide hormones to experimentally made amnestic rats showed obvious recovery of memory [Bela Bohus et al., Brain Research 157 (1978) 414-417]. It is also reported that such peptide hormones showed a similar effect in clinical tests for human [H. Weingartner et al., Science 211, (1981), 601-603]. It is known that all of these peptide hormones contain proline and exist in brain. These peptide hormons are anticipated to be metabolized with internal peptidase among which proline-specific endopeptidase (post-proline cleaving enzyme) are supposed because of their specific nature to participate in the metabolism of many proline-containing peptide hormons.
Various approaches have been made from the past to proline-specific endopeptidase inhibitory agents. Among these approaches, a special concern is paid to the fact that N-benzyloxycarbonylglycyl-L-prolyl-chloromethane and N-benzyloxycarbonyl-L-prolylprolinal possess a strong inhibitory action to the endopeptidase [T. Yoshimoto et al., Biochem. 16 (1977), 2942-2948 and S. Sherwin et al, Neurochem. Wilk et al., J. Neurochem. 41 (1983), 69-75]. In this aspect, therefore, further approach is demanded to study biochemical activities of such endopeptidase inhibitory agents.